A wave of thunderstorms started about 70 fires in California on July 23, but light rain and cooler temperatures prevented them from spreading, and most were quickly contained by firefighters

Officials said the thunderstorms are more dangerous because of higher temperatures, lower humidity, less likelihood of rain and predicted high winds. Scant snowpack and extra-dry brush are also making the Sierra Nevada range more vulnerable to fires.

"If we do get lightning strikes," said National Weather Service meteorologist Eric Kurth, "then we could have some major fires if they are not quickly attacked by the firefighters."

Firefighters are battling several wildfires around the state, including one that has scorched 7 square miles in the Plumas National Forest and another that has forced the evacuation of about 100 homes in the Shasta-Trinity National Forest.